This section is intended to provide a background or context to the invention recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The optoelectronic properties of metal oxides, such as zinc oxide (ZnO), make them promising candidates for use in photovoltaic devices, field emission devices, and sensors (gas, UV, and biological). For example, zinc oxide is a multifunctional semiconducting material with a direct, wide bandgap energy of 3.4 eV, which makes it transparent in visible light (ZnO absorbs in the ultraviolet (UV) to blue wavelengths). Additionally, ZnO has a resistivity that may be tuned from a semi-insulating material to semi-metallic material by known doping techniques and one of the highest piezoelectric response times of any semiconductor. Thus, thin film and bulk ZnO materials have been explored for various applications in electronics, optics, photonics, and biologics.
Conventional techniques for fabricating ZnO-based devices involve nanowire growth, nanoparticles, and thin films. ZnO nanowires are semiconducting particles having a high aspect ratio, with cross-sectional diameters less than 1 μm, and lengths as long as tens of microns. Aside from problems in fabricating ZnO nanowires as a material, which include catalytic poisoning, precursor degradation, and isotropic growth, ZnO nanowire-based devices also suffer from requiring specialized substrate treatments, needing both a top and bottom electrode, limited growth geometries, and customized topologies which make ZnO nanowire growth challenging.
ZnO nanoparticle-based devices face similar setbacks in optoelectronic applications, suffering from unreliable electrical contacts due to self-assembling positional arrangements of the nanoparticles, a need for both a top and bottom electrode, and difficulties in integrating nanoparticle materials in large arrays. A third alternative for integrating ZnO into optoelectronic applications is by thin film deposition, typically using expensive semiconductor tools, and techniques such as physical vapor deposition (PVD), chemical vapor deposition (CVD), pulsed-laser deposition, molecular beam epitaxy, spray-pyrolysis, and electro-chemical deposition techniques. Devices based on ZnO thin films often require special substrates, are limited to top electrode configurations, and are limited in application. For example, ZnO thin films are not easily compatible for photonic devices.
A need exists for improved technology, including polymer-hybrid electro-optic devices and a method of fabricating the polymer-hybrid electro-optic device.